Fascinating paper from the Astronomy and Astrophysics journal on the most distant comet observation with a telescope.

Use the 2.2m ESO telescope at La Silla, the observers have stacked 26 x 180s exposures of the distant comet Hale Bopp. The distance is around 30.7 Astronomical units, or 2,850,000,000 miles in more local terms.

Comet Halley had been observered at around 27 AU distance, but these new observations beat that record.

Objects the size of Hale-bopp (around 30km) are very faint that this extreme distance, researchers give a magnitude estimate of around magnitude 24.5

Comet Hale Bopp has been extremely active, but these recent telescope observations show that the comet activity is now in rapid decline. Some scattering from a light coma was detected, but the comet is now almost in deep freeze.

We ought to be able to continue tracking Hale-Bopp with the worlds largest telescopes until around the year 2020 when the magnitude falls below mag 30 and pickign the comet out of the background galaxies becomes impossible.

Although I enjoy a naked eye observation of a comet as much as the next person, I've never been particular interested in imaging them. However, this type of observation is in a different class of astrophotography. Simply finding the damn thing must be a challange. The researchers noted that the comet appeared slightly out of the predicted position in the sky, but comet revealed its nature by a slow movement against the background stars.

Hale-bopp wil be back in our skys in the year 4385, so don't wait up!

Paper reference :A&A 531, A11 (2011)
DOI: 10.1051/0004-6361/201116793

Frozen to death? Detection of comet Hale-Bopp at 30.7 AU